Thermionic tube



lMaly 14, 1946. w. w. Emil. ETAL THERMIONIC TUBE Filed Oct. 10, 1941 H 6 HU n E n H OWc. N T M R WMA. m Vm T mL A l. R WJ W m T *Patented May 14, 1946 'rnEaMIoNlc TUBE william w. Enel and Jack A. McCullough, sin' Bruno, Calif., assignors to Eifel-McCullough, Inc., San Bruno, Calif., a corporation of Calir fornia Application Octoberl, 1941, Serial No. 414,503

9 Claims.

Our invention relates to a vacuum tube having a thermionic operating unit including electrodes such as cathode, grid and anode.

It is among the objects of our invention to provide an improved vacuum tube construction, particularly adapted for high frequency work.

Another object is to provide improved means for mounting and establishing electrical connections with the electrodes.

A further object of our invention includes the provision of a tube in which the design of envelope and arrangement of leads facilitates the assembly and alignment of the electrodes.

The invention possesses other objects and features of advantage, some of which with the foregoing, will be set forth in the following description of our invention. Itis to be understood that we do not limit ourselves to this disclosure of species of our invention, as we may adopt variant embodiments thereof within the scope of the claims,

Referring to the drawing:

Figure 1 is a vertical sectional view through the envelope of a. tube embodying the improvements of our invention, parts of the internal structure being shown in section and parts in elevation: and

Figure 2 is a similar view taken in a plane through the envelope at right angles to that of Figure 1.

In terms of broad inclusion, our thermionic tube comprises an envelope containing coaxial electrodes including a cathode, grid and anode. The anode is supported on a lead extending through the top of the envelope and disposed coaxially with the electrodes, While the grid is 'supported on a pair of aligned leads extending through the sides of the envelope and disposed transversely of the axis. The cathode comprises two filament sections supported at a mid point by a standard projecting from a stem of the envelope, and a shield connected with the standard is provided about the stem. The envelope is preferably cylindrical in shape, having a c ir- Grid l is preferably of the ordinary cage type having vertical wires terminating at a base ring disposed adjacent the lower end of the anode.

Cathode 3 preferably comprises two coaxial sections or coils connected at the bottom to leads 3 welded to extension leads l I projecting through pinch l2 of a reentrant stem I3 at the lower portions of the envelope. Since the tube is designed for high frequency work the leads I l lpreferably project directly through the base ofthe tube to avoid the congestion in the usual pronged base structures. Leads ll are preferably somewhat larger than the inner leads 9 for purposes of rigidity. These leads are made of metallic rods, such as tungsten. A central standard or rod Il is also sealed in the stem, and is secured to the upper mid portion of the filament for supporting the latter.

A cup-shaped metallic shield I6 is provided on the stem to protect it against heat and electron bombardment. Leads 9 project througha slot in the top of the shield, and the shield is grounded to the filament standard I4 by welded lips l1. These lips are fairly wide and also function to cover the central portions of the slot, leaving only small clearances about leads 9. Apertures I8 in the sides of the shield provide openings through which air may be quickly withdrawn during the exhaust process.

Envelope 2 is preferably cylindrical in shape, having a top dome I9 and joined to stem I3 by a base flare 2l. In a tube having an anode diameter of about 3A inch the diameter of the cylindrical envelope wall is preferably about 2 inches. This gives a relatively close spacing between the envelope side walls and an electrode for purposes of making short leads. Additional clearance is provided about the anode by a circumferential bulge 22 preferably lying substantially between planes defined by the ends of the anode. This removes the glass from the heat zone about the anode; the annular recess formed by the bulge providing the greatest spacing at the mid section of the anode where heat is greatest.

Anode lead 23 extends through a seal 24 in the dome of the envelope and is disposed coaxial with the electrodes. The anode is supported on the inner end of this lead by a bracket 26 made in two pieces welded to cap 8 and forming a sleeve embracing lead 23 with flanges 21 for heat radiation. The flanges are preferably provided with inclined slits with portions bent out to form heat radiatingpoints 2l to reduce heat conduction from the anode to the glass seal.

A pair of aligned leads 29 are provided for the grid, which leads are disposed in the plane of and transversely of the .electrode axis adjacent the lower end of the anode. These grid leads extend through seals on horns 30 arranged on opposite sides of the cylindrical envelope wall below bulge 22. The grid is supported on the inner ends of leads 29 by brackets 3| each secured at one end to ring 8 and at the other end to one of the leads. Brackets 26 and 3| of the anode and grid are made of a ductile material such as tantalum,

while leads 23 and 29 are rigid rods of say tungsten,

The\structure above described provides a pair of widely spaced grid leads through either one or both of which electrical c onnections may be made with the grid. Utilizing the dual leads the grid may be interposed in anexternal circuit so as to balance capacity.

Alignment of the grid leads provide maximum spacing between them; and their being positioned below the bulge and at a point where the cylindrical wall of the envelope lies close to the electrode axis provides short electrical connections.

Our tube is easily fabricated and the electrodes are readily assembled in proper alignment because the electrodes and cylindrical envelope are all concentric, and because the transversely extending grid leads are aligned and lie in the same plane with the axes of the electrodes, anode lead and envelope. Furthermore, the cylindrical envelope with its annular bulge 22 provides a compact tube having improved mechanical strength.

We claim:

1. In a thermionic tube, an envelope, an anode and grid in the envelope, a lead disposed longitudinally of the anode axis and extending through the envelope, a pair of leads disposed transversely of said axis and extending through the envelope, means adjacent one end of the anode for supporting it on the iirst mentioned lead, and means adjacent the other end of the anode for supporting the grid on said pair of leads.

2.s In a thermionic tube, a substantially cylindrical envelope, an anode and grid in the envelope, said envelope having a circumferential bulge disposed about the anode, a lead disposed longitudinally of the anode axis and extending through the envelope above the bulge, a pair of leads disposed transversely of said axis and extending through the envelope below the bulge, means for supporting the anode on the inner end of the iirst mentioned lead, and means for supporting the grid on the inner ends of said pair of leads. l

3. In thermionic tube, a substantially cylindrical envelope, an anode and grid in the envelope, said envelope having a circumferential bulge disposed about the anode, a lead disposed longitudinally of the anode axis and extending through the envelope above the bulge, a pair of leads disposed transversely of said axis and extending through the envelope below the bulge.

means for supporting the anode on the inner end of the rst mentioned lead, means for supporting the grid on the inner ends ofsaid pair of leads, a cathode in the envelope, and leads for the cathode extending through the lower portions of the envelope.

4. In a thermionic tube, an envelope, an anode and grid in the envelope, a lead disposed longitudinally of the anode axis and extending through the envelope, a pair of aligned leads disposed transversely of said axis and extending through the envelope, means adjacent one end of the anode for supporting it on the iirst mentioned lead, and means adjacent the other end of the anode for supporting the grid on said pair of leads.

5. In a thermionic tube, an envelope, an anode and grid in the envelope, a lead disposed longitudinally of the anode axis and extending through the envelope, a pair of leads disposed at right angles to said axis and extending through the envelope, means adjacent one end of the anode for supporting it on the first mentioned lead, and means adjacent the other end of the anode for supporting the grid on said pair of leads.

6. In a thermionic tube, an envelope, an anode and grid in the envelope, a lead disposed longitudinally of the anode axis and extending through the envelope, a pair of aligned leads disposed transversely of said axis and extending through the envelope, said grid having a free end terminating adjacent one end of the anode, means adjacent said anode end for supporting it on the first mentioned lead, and means adjacent the other end of the anode for supporting the grid on said pair or leads.

7. A thermionic tube comprising an envelope, an electrode in the envelope, a. lead extending through the envelope, means supporting the electrode on the lead, and a heat radiating iin extending longitudinally of the lead, said iin having a slit therein angularly disposed to the lead axis to retard ilow of heat from the electrode toward the point where the lead is sealed to the envelope.

8. A thermionic tube comprising an envelope, a tubular anode in the envelope, a cap secured to an end of the anode, a lead extending through the envelope, and a bracket on the cap for supporting the anode on the lead, said bracket having a heat radiating iin thereon extending longitudinally of the lead.

9. A thermionic tube comprising an envelope, a tubular anode in the envelope, an anode lead disposed longitudinally of the anode axis and extending through the envelope, a cap on one end of the anode connected to said lead, a grid associated with the anode, a grid lead extending through the envelope along a line angularly disposed to said axis, and means adjacent the anode end opposite said c ap for connecting the grid to said grid lead.

WILLIAM W. EI'I'EL. JACK A. MCCULLOUGH. 

